1.1.3 Storage devices

Question 1

What is optical storage?

Answer 1

Devices that are read from and written to using lasers. Binary information is represented by portions of the disc which either reflect or scatter the incident laser light written in spiral tracks on the disc’s surface.

A microscopic view of the surface of a CD. The portions which are recessed, called pits, scatter light whereas the flat portions, called lands, reflect light. Pits represent a 0 and lands represent a 1.

Question 2

What is magnetic storage?

Answer 2

Devices which store information magnetically represent binary information using two magnetic states: polarised and unpolarised. If a portion of magnetic material is polarised, all magnetic poles align and can be read by a read/write read passing over the region. If an area is not polarised, magnetic poles are randomly scattered and produce a different reading on a read/write head. These two states can represent 1 and 0, allowing any information to be represented in binary form.